EP0047702A1 - Distributor for a vehicle brake system, particularly for vehicles in agricultural usage - Google Patents

Abstract

1. A distributor for a brake system of a vehicle comprising a pair of master cylinders (102, 202) controllable separately, one of said master cylinders being connected to a brake motor (110) associated to a wheel at the right side of the vehicle and the other master cylinders being connected to a brake motor (210) associated to a wheel at the left side of the vehicle, a pair of brake motors (112, 212) associated to wheels situated at the right and at the left of the vehicle, and a distributor (113, 313) connected at one side to said pair of master cylinders (102, 202) and at the other side to said pair of brake motors (112, 212), said distributor permitting admission of fluid under pressure to said motors of said pair only upon a simultaneous actuation of said master cylinders, said distributor being characterized in that it comprises a pair of identical valves (134, 234; 334, 434) each comprising an inlet orifice (130, 230; 330, 430) connected to one of the master cylinders, an outlet orifice (132, 232; 332, 432) connected to one of the motors of said pair, a valve seat (136, 236; 336, 436) between said orifices, and a movable closure element (150, 250; 350, 450) normally spaced from said seat by a predetermined distance (b) and responsive to a small pressure at the inlet orifice to engage said seat, the distributor comprising a mechanical connection (138, 238, 157; 338, 438) between the closure elements of the two valves upon which said closure elements act in opposite directions, said mechanical linkage having a lost motion (2a) the length of which is greater than said predetermined distance (b) and smaller than twice of said predetermined distance.

Description

The present invention relates to a distributor for a vehicle braking system.

In certain vehicles, in particular for agricultural use, it is common to provide two independent brake master cylinders, one serving a brake motor associated with the right rear wheel of the vehicle and the other serving a brake motor associated with the left rear wheel of the vehicle, the two master cylinders can be used separately to provide assistance with changes in direction of the vehicle or simultaneously to ensure the actual braking of the vehicle. In the latter case, in order to balance the braking forces, provision is made for the coupling of the two pedals of the two master cylinders.

When the vehicle also includes a pair of brake motors associated with the front wheels, or a pair of brake motors associated with the wheels of a trailer, it is necessary to differentiate, with regard to this pair of brake motors, "slowdown" braking actions, during which all of the vehicle's brake motors (and possibly of the trailer) must be supplied with pressurized fluid, "directional" braking actions, during which only one of the The vehicle's rear wheel brake motors must be supplied with pressurized fluid.

To this end, it is known to incorporate into the vehicle braking system a distributor connected on the one hand to the two master cylinders and on the other hand to the brake motors of said pair, said distributor only allowing the admission of fluid under pressure to said engines of said pair only during a simultaneous actuation of said master cylinders.

We know from the German patent application N ° DE 05 2 059 037, a distributor performing this function. However, this distributor has the following drawback: the two brake motors constituting said pair are supplied together from a single one of two master cylinders, which makes it necessary to provide an equalizer assembly for intercommunication of fluid between the two master cylinders. Indeed, it is not possible to provide a simple coupling between the two pedals because in this case, the two master cylinders would serve circuits that are too asymmetrical.

In addition to the complexity of the master cylinders which results from this arrangement, it is also noted that it presents a serious danger in the event of rupture of one or the other of the circuits since the braking system can then be completely emptied.

• une paire de maître cylindres à commande séparée reliés l'un à un moteur de frein associé à une roue située à droite du véhicule et l'autre à un moteur de frein associé à une roue située à gauche du véhicule, une paire de moteurs de freins associés à des roues situées à droite et à gauche du véhicule et un distributeur relié d'une part à ladite paire de maître cylindres et d'autre part à ladite paire de moteurs de freins, ledit distributeur ne permettant l'admission de fluide sous pression auxdits moteurs de ladite paire que lors d'un actionnement simultané desdits maître cylindres, ledit distributeur étant caractérisé en ce qu'il comprend une paire de valves identiques comprenant chacune : un orifice d'entrée relié à l'un des maître cylindres, un orifice de sortie relié à l'un des moteurs de ladite paire, un siège de valve entre lesdits orifices et un élément de fermeture mobile normalement éloigné dudit siège d'une distance donnée et sensible à une faible pression audit orifice d'entrée pour venir en contact avec ledit siège, ledit distributeur comprenant une liaison mécanique entre les éléments de fermeture des deux valves, sur laquelle ces éléments de fermeture agissent de manière antagoniste, ladite liaison mécanique comportant une course morte supérieure à ladite distance donnée et inférieure au double de cette même distance donnée.

In order to overcome these drawbacks, the present invention provides a distributor for a vehicle braking system comprising:

• a pair of separately controlled master cylinders, one connected to a brake motor associated with a wheel located to the right of the vehicle and the other to a brake motor associated to a wheel located to the left of the vehicle, a pair of motors brakes associated with wheels located on the right and left of the vehicle and a distributor connected on the one hand to said pair of master cylinders and on the other hand to said pair of brake motors, said distributor only allowing the admission of fluid under pressure to said motors of said pair than during simultaneous actuation of said master cylinders, said distributor being characterized in that it comprises a pair of identical valves each comprising: an inlet orifice connected to one of the master cylinders, a outlet port connected to one of the motors of said pair, a valve seat between said ports and a movable closure element normally distant from said seat by a given distance and sensitive to a low pressure at said inlet port rée to come into contact with said seat, said distributor comprising a mechanical connection between the closure elements of the two valves, on which these closure elements act in an antagonistic manner, said mechanical connection comprising a dead travel greater than said given distance and less than double this same given distance.

• - La figure 1 est une représentation schématique d'un système de freinage incorporant un distributeur selon l'invention ;
• - la figure 2 est une vue en coupe d'un premier mode de réalisation d'un distributeur selon l'invention, et
• - la figure 3 est une vue en coupe d'un second mode de réalisation d'un distributeur selon l'invention.

The invention will now be described with reference to the accompanying drawings, in which:

• - Figure 1 is a schematic representation of a braking system incorporating a distributor according to the invention;
• FIG. 2 is a sectional view of a first embodiment of a dispenser according to the invention, and
• - Figure 3 is a sectional view of a second embodiment of a dispenser according to the invention.

The braking system shown schematically in Figure 1 consists of a pair of master cylinders 102 and 202 which can be actuated either separately by means of two pedals 104 and 204 respectively, or together by means of a coupling pedal 105 Each master cylinder has a tank 106-206, as well known. The master cylinder 106 is connected by a conduit 108 to a brake motor 110 associated with the right rear wheel of the vehicle, and, in the same way, the master cylinder 206 is connected by a conduit 208 to a brake motor 210 associated with the vehicle's rear left wheel. The vehicle further comprises a pair of brake motors 112 and 212 respectively associated with the right front wheel and the left front wheel. A fluid distributor 113 is connected on the one hand to the two master cylinders 102 and 202 and on the other hand to the two brake motors 112 and 212, the structure and the function of this distributor being the object. of the description which follows.

Figure 2 is a partial sectional view of a first embodiment of a dispenser according to the invention.

The distributor 113 comprises a housing 115 symmetrical with respect to an axis XX, and only the elements situated on one side of this axis will be described, the others bearing the same reference numbers, increased by 100.

The housing has a stepped bore 114 formed by a small diameter portion 116 and a large diameter portion 118, the latter being closed by means of a plug 120. As shown, the plug has a cylindrical axial recess 122 and a peripheral groove 124, connected by a passage 126. The bore portion 118 and the plug 120 define a cavity 128 into which open an inlet orifice 130, in the vicinity of the bottom of this bore, and an outlet orifice 132, at the level of the groove 124 of the plug 120. In the cavity 128 is mounted a valve 134 in the following manner: an annular valve seat 136, made of elastomeric material, is mounted in leaktight manner in the bore 118 and in contact with the end of the plug 120. A piston 138 is slidably mounted in leaktight manner in the bore portion 116 and projects at one of its ends 140 outside the housing and at the other end 142 in the cavity 128. This last end is composed a radial flange 144, in which axial notches 146 are formed, a narrowed part 148 and an enlarged part forming a valve shutter 150, the diameter of which is equal to the diameter of the bore part 116 and less to that of the recess 122. It will be noted that the valve seat 136 has an internal diameter greater than the diameter of the narrowed part 148 of the piston and less than the diameter of the valve shutter 150. Finally, a return spring 152 repels the piston 138 pressing against the plug 120, thus defining a so-called rest position in which the valve shutter 150 is distant from the valve seat 136 by a distance b. As shown, the spring 152 bears on the one hand on the flange 144 and on the other hand on an annular cage 154 surrounding the piston 138 and trapping a seal 156 ensuring the seal between the piston 138 and the bore portion 116 .

Facing the ends 140 and 240 of the pistons 138 and 238, the distributor comprises a mechanical link 157. This comprises a plunger 159 inserted into a hole 161 in the housing coaxially with the axis XX and locked in position by a needle screw 163. A pivot 165 is fixed perpendicular to the plunger 159 and a beam 167 is pivotally mounted around the pivot 165. This beam comprises two arms 166 and 266 which are separated, at rest, from each of the pistons 138 and 238 by a distance a. Double this distance, or 2a, will hereinafter be called the dead stroke of the mechanical link 157. A cap 169 mounted between the housing and the plunger 159 protects the mechanical link 157 against external agents.

The distances a and b are chosen so as to verify the relation: a <b <2a, for reasons which will be explained later.

• - En cas de freinage "directionnel", par exemple par actionnement du maître cylindre 102 seul, au moyen de la pédale 104, la pression engendrée dans ce maître cylindre est transmise d'une part au moteur de frein 110 pour assurer le freinage de la roue arrière droite du véhicule, et d'autre part à l'orifice d'entrée 130 du distributeur 113. Dès que cette pression atteint une faible valeur, le ressort 152 étant déterminé en conséquence, le piston 138 se déplace vers l'extérieur du boîtier. Dès que l'amplitude du déplacement du piston 138 atteint la valeur "b", l'obturateur de valve 150 vient en contact avec le siège 136, interrompant ainsi la liaison avec le moteur de frein 112 de la roue avant droite du véhicule. On remarquera que la liaison mécanique 157 permet un tel déplacement du piston 138. En effet, la distance b étant supérieure à la distance a, l'extrémité 140 du piston 138 vient repousser le bras 166 du fléau 167, cependant que l'autre bras 266 du fléau ne peut venir au contact de l'extrémité 240 du piston 238 puisque cette même distance b est inférieure à la course morte 2a. La valve 134 étant ainsi fermée, la pression régnant à l'orifice de sortie 132 et transmise au moteur de frein avant droit 112 restera égale à la faible valeur mentionnée ci-avant, et qu'on choisira de manière à rester en dessous du seuil d'actionnement du frein en question, quelque soit la pression engendrée dans le maître cylindre 102.
  En résumé, l'actionnement du maître cylindre 102 seul provoque le seul freinage de la roue arrière droite du véhicule.
  Réciproquement, l'actionnement du maître cylindre 202 seul provoque le seul freinage de la roue arrière gauche du véhicule.
• - tn cas de freinage "de ralentissement", par actionnement simultané des deux p-xfales 104 et 204, ou, mieux, par actionnement de la pédale d'accouplement 105, les deux maîtres cylindres délivrent du fluide sous pression d'une part aux moteurs de frein 110 et 210 pour assurer le freinage simultané des deux roues arrière du véhicule, et d'autre part aux deux orifices d'entrée 130 et 230 du distributeur 113. Les deux pistons sont alors repoussés vers l'extérieur du boîtier. Dans ce déplacement, chacun des deux pistons 138, 238 vient en butée avec le bras 166, 266 du fléau qui lui correspond et s'immobilise dans cette position. Puisque les deux pistons ne se sont déplacés que d'une distance a, inférieure à b, les deux valves 134 et 234 restent ouvertes et le fluide sous pression délivré par les maître cylindres 102 et 202 est également admis aux moteurs de frein-des roues avant 112 et 212 respectivement.

The distributor 113 is mounted on the vehicle and connected to the other members of the braking system: the master cylinders 102 and 202 being connected respectively to the inlet ports 130 and 230 and the brake motors 112 and 212 being connected respectively to the outlet ports 132 and 232 (Figure 1). During various braking actions, the distributor 113 operates as follows:

• - In the case of "directional" braking, for example by actuation of the master cylinder 102 alone, by means of the pedal 104, the pressure generated in this master cylinder is transmitted on the one hand to the brake motor 110 to ensure the braking of the right rear wheel of the vehicle, and on the other hand to the inlet orifice 130 of the distributor 113. As soon as this pressure reaches a low value, the spring 152 being determined accordingly, the piston 138 moves outwards from the housing. As soon as the amplitude of movement of the piston 138 reaches the value "b", the valve shutter 150 comes into contact with the seat 136, thus interrupting the connection with the brake motor 112 of the right front wheel of the vehicle. It will be noted that the mechanical link 157 allows such displacement of the piston 138. In fact, the distance b being greater than the distance a, the end 140 of the piston 138 pushes the arm 166 of the beam 167, while the other arm 266 of the beam cannot come into contact with the end 240 of the piston 238 since this same distance b is less than the dead travel 2a. With the valve 134 thus closed, the pressure prevailing at the outlet orifice 132 and transmitted to the right front brake motor 112 will remain equal to the low value mentioned above, and which will be chosen so as to remain below the threshold. actuation of the brake in question, whatever the pressure generated in the master cylinder 102.
  In summary, the actuation of the master cylinder 102 alone causes only braking of the right rear wheel of the vehicle.
  Conversely, actuation of the master cylinder 202 alone causes the vehicle's rear left wheel to brake only.
• - in the case of "deceleration" braking, by simultaneous actuation of the two p-xfales 104 and 204, or, better, by actuation of the pedal 105, the two master cylinders deliver pressurized fluid on the one hand to the brake motors 110 and 210 to ensure the simultaneous braking of the two rear wheels of the vehicle, and on the other hand to the two inlet ports 130 and 230 of the distributor 113. The two pistons are then pushed towards the outside of the housing. In this movement, each of the two pistons 138, 238 abuts with the arm 166, 266 of the beam which corresponds to it and stops in this position. Since the two pistons have only moved a distance a, less than b, the two valves 134 and 234 remain open and the pressurized fluid supplied by the master cylinders 102 and 202 is also admitted to the brake-wheel motors before 112 and 212 respectively.

In summary, the simultaneous actuation of the two master cylinders 102 and 202 causes the braking of the four wheels of the vehicle.

It will be noted that this braking of the four wheels of the vehicle can also be obtained following a directional braking by simply actuating the second pedal, either directly, or by means of the coupling pedal.

The embodiment of the dispenser illustrated in FIG. 3 includes a large number of elements identical to those of the embodiment already described, and to which the same reference will be assigned, increased by the value 200.

The distributor 313 comprises a housing 315, which can, as shown by the dotted line, be made in two parts 315 and 415 fixed to each other by any suitable means. In this embodiment, the bores 314 and 414 are coaxial, the bore portions 316 and 416 forming a single bore. The mechanical connection with dead travel "2a" is here simply achieved by the fact that the ends 340 and 440 of the pistons 338 and 438 are separated at rest by a distance equal to "2a". The space 371 between the two pistons is connected to the atmosphere by a conduit 373.

The description of the operation of the distributor 313 will not be repeated in detail. It will only be noted that during "directional" braking, for example by means of the master cylinder 102, the piston 338 is free to move in the direction of the piston 438 until the valve 334 is closed, while during 'braking "deceleration", the two pistons move towards each other, until mutual contact, a distance a, without causing the closure of the valves 334 and 434.

In the foregoing, it has been assumed that when the two master cylinders 102 and 202 are actuated by means of the coupling pedal 105, the pressures generated have a very small difference so that during braking " normal ", the vehicle brakes are all supplied at substantially the same pressure, the vehicle therefore remaining stable on its path. In the event that this pressure difference turns out to be too great and the stability of the vehicle is compromised, it will be necessary to provide a pressure balancer between the two master cylinders, as well known in the art.

Claims (9)

1. Distributor for a vehicle braking system comprising: a pair of separately controlled master cylinders, one connected to a brake motor associated with a wheel located to the right of the vehicle and the other to a brake motor associated with a wheel located on the left of the vehicle, a pair of brake motors associated with wheels located on the right and left of the vehicle and a distributor connected on the one hand to said pair of master cylinders and on the other hand to said pair of engines brakes, said distributor allowing the admission of pressurized fluid to said motors of said pair only during a simultaneous actuation of said master cylinders, said distributor being characterized in that it comprises a pair of identical valves each comprising: an orifice inlet connected to one of the master cylinders, an outlet orifice connected to one of the motors of said pair, a valve seat between said orifices and a movable closure element normally distant from said seat from a istance given and sensitive to a low pressure at said inlet orifice to come into contact with said seat, said distributor comprising a mechanical connection between the closing elements of the two valves on which these closing elements act in an antagonistic manner, said mechanical connection comprising a dead stroke greater than said given distance and less than twice this same given distance. 2. Dispenser according to claim 1, characterized in that each of said valves comprises a housing in which a cavity is defined, said inlet and outlet orifices opening into said cavity, said closure element being carried ^by a piston mounted slidingly sealingly through a wall of said cavity and one end of which is pr-o-flows outside of said housing, the housings of the two valves being fixed to one another. 3. Distributor according to claim 2, characterized in that the two housings are defined in a single element. 4. Distributor according to either of claims 2 or 3, characterized in that each piston is biased towards the inside of the corresponding housing by a return spring. 5. Distributor according to any one of claims 2 to 4, characterized in that the two pistons are coaxial, their ends being mounted face to face and separated by a distance equal to said dead stroke. 6. Distributor according to any one of claims 2 to 4, characterized in that the two pistons are parallel and define between them an axis of symmetry, their ends projecting into the same steering, said mechanical connection comprising a beam with two symmetrical arms articulated around a pivot perpendicular to said axis of symmetry, the ends of said pistons being distant from said arms by a distance, measured parallel to said axis, equal to half of said dead travel . 7. Distributor according to claim 6, characterized in that the axial position of said pivot is adjustable. 8. A dispenser according to claim 7, taken in combination with claim 3, characterized in that said single element comprises a bore coaxial with said axis of symmetry, said pivot being fixed perpendicular to a plunger slidingly mounted in said bore, said plunger being locked in position by a needle screw. 9. A dispenser according to any one of claims 2 to 8, characterized in that said closure elements have a section equal to that of said pistons on which these closure elements are carried.

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